Relation of Usage to the Occurrence of Cotton and Rice Herbicides in Three Streams of the Mississippi Delta
Received for review April 6, 1998 Revised manuscript received July 24, 1998 Accepted September 2, 1998 Abstract: During the 1995 growing season water samples were
collected from three streams in the Mississippi delta and
were analyzed for selected cotton and rice herbicides
and metabolites. The purpose of the study was to relate
the use of these herbicides to their occurrence in streams
of the delta, to describe how the geochemistry of these
herbicides affects their occurrence, and to report the
occurrence of selected metabolites. The total concentration
of eight herbicides and their metabolites exceeded 5
Download the full text:
PDF |
HTML
g/L throughout most of the growing season with a median
total of 15 g/L. The order of occurrence was molinate
> fluometuron > cyanazine > metolachlor > norflurazon
> atrazine > prometryn > propanil. The distribution
and duration of the total herbicide concentration found in
this study are much different from that found in regional
studies of herbicides in the U.S. Midwest. In the Midwest,
the total herbicide concentration in surface water
showed a sharp peak during the spring immediately after
application of herbicides to crops, followed by a gradual
decrease. In the Mississippi delta, the total herbicide
concentration in surface water was more sustained, with
multiple peaks due to different application times and
postemergent applications to cotton and rice.
